Pressure balanced pump



Jan. 15, 1963 J. c. HOOVER 3,073,254

PRESSURE BALANCED PUMP Filed Deo. 24, 1959 2 sheets-sheet 1 w i s Si M/NVENTOR JOHN C. HOOVER? @YW EMM ATTORNEY Jan. 15, 1963 J. c. HOOVER3,073,254

PRESSURE BALANCED PUMP Filed Deo. 24, 1959 2 Sheecs--Sheei'I 2 /A/ETCEA/723 0F LA-n AITOQNEY 3,073,254 PRESSURE BALANCED PUMP John C.Hoover, St. Petersburg, Fla., assigner to United Aircraft tlorporation,East Hartford, Conn.,'a eorperlag tion ofpDelaware FildDee. 24, 1959,Ser. No. 861,931

` v"SCainita (Cl. S-162) This invention relates to piston pumps andmore` particularly to fluid pumps'having a rotor carrying the pistonsandin which 'the pistons reciprocate.

It is a feature of this invention to provide a pressurebalancingarrangementwhereby fluid underV pressure is directed from ahigh-pressure source through a fixed laminar restriction and to theantipumping end ofthe piston where it is conducted to la reactionsurface such as a bearing so that bearing forces are reduced.

It is another feature of this invention to provide the above pressurebalancing in an axial pistonpurnp having a xed reaction bearing surface.

It is another feature of this invention to provide a predeterminedspacing between the piston and piston walls to forma fixed restrictionwhich connects inturn to an annulus around-the piston for subsequentcommunication with passages in the piston rod which' lead to thereaction surface.

It is still a further feature of this invention to provide means formaintaining a fluid film between the fixed reaction bearing surface andunitary drive plate surface so 'that the high friction normallyassociated with bearing surfaces is reduced to a minimum during startingregimes of the pump.

It is another feature of this invention to provide a unitary drive platethat'has axial motion relative to the xed thrust bearing so thatrelative distance therebetween lforms a variable fluid escape path.

It is another feature of this invention to provide an axial piston pumphaving a thrust member which operatively receives the antipumping endsof the pist-on rods and includes a surface comprising a plurality ofpressure wells receiving the metered uid under pressure for pressurebalancing the pump, these wells forming pressure chambers in relation tothe adjacent flat bearing or reaction surface.

It is a further feature of this invention to provide pressure Wellswhich are so located with respect to their respective piston rods suchthat the resultant center of pressure is coincident with or radiallyspaced outwardly with respect to the location of the major forceresisting this pressure load. v

It is a further featurel of this invention to provide a plain axialbearing and a plain radial bearing with the radial bearing beingparticularly aligned to avoid eccentric loading.

These land other features of this invention will become readily apparentfrom the `following detailed description of the drawings in which: 1 isa detailed cross-sectional illustration of the pump assembly embodyingthe features of this invention;

2 is an enlarged detailed cross-sectional showing of the piston rodassembly including its connection to the thrust plate;

FIG. 2a is an enlarged detail of a portion of the FIG. 2 showing thevparts in a slightly exaggerated position;

FIG. 3 is an enlarged detailedy showing of the bottom of the unitarythrust plate; and Y FIG. 4 is a partial showing of a side view of FIG. 3schematically illustrating the tilt-balancing forces.

Referring to FIG. 1, the pump is shown as having an upper casing 10 anda lower base casing 12 from which protrudes at the left side a toothednumber 14 for drivftes aient 3,073,254 Patented Jan.. 15, 1963 ing thepump. The member 14 includes a shaft 16 having splines 1S for drivingthe unitary thrust or drive plate' 20. The unitary thrust plate 20'includes a number of peripherally spaced ball-receiving sockets22 whichreceive the balls 24 of the antipumping end of each piston'rod 26. Theunitary drive plate adjacent its left endv includes an elongated spline30 which'also through the spline 32 drives a coupling 343V carrying abeveled gear 36. -The beveled gear 36 engages a cooperating gear. 38-for driving the shaftextension ttlwhich via the splines 42 drivesbarrel-likeV rotor 44. The axis of the rotor 44 is atr an angle withrespect'to the drive platel 20 andV its adjacent bearing 120y such thatas thebarrel rotates Vthe pistn rods 26 are reciprocated therebyinducing a pumping Irio-4 tion to the pistons 50.k A Valve plate 60 issuitably held intoengagement with the top pumping end ofthe rotor 44 andis held against continued rotation by means yof. a spline connection 62leading to a control shaft 64. The control shaft 64 isrnountedonsuitable bearings 66'and 63 and carries a pinion 70 which 4isp engagedyby one or more racks 72 which can'in turn be actuated oy a suit# ableservo unit. The servo unitis intended to rotate the valve plate 6@ so asto interconnect onejor, more pistons either to theV inlet or the outlet82 or to connectA certain pistons to each other. A control mechanism ofthis type is more clearly illustrated and describedl in cepending patentapplication Serial No. 821,180,v filed June 18, 1959, now Patent No.3,050,014 issued August 21,1962, by Richard N. Sullivan. f

With high pumping loads, normally, the antipumping endo-f the piston,piston-rod assembly would have tobe engaged and supported by thrustAhearings of substantial weight and size. However, provision is madeforpres` sure balancing the assembly so that a lightweightr plainbearing can be utilized: in place of the much heavier antifriction-typeball bearings or the like. To, this end, each piston 50 (see also EIG.2) has a land portion 9,0 which is meticulously .machined andlapped'with respect to its adjacent rcylinder wall so as toI form afirst fxedl orifice 92, better seen in FIG. 2. The fixed orifice 92;thus formed is continuously wiped during the. piston reciprocation whichtends to make it a self-cleaning ca'pillaryf restriction. Therestriction is of aA predetermined size and length so that under maximumpressure operation of the pumpv a predetermined pressure drop willloccur thereacross. During operation, high-pressure uidl from the pumpingchamber 94 ows through the fixed restriction 90 and thence to an annulus96 leading'to a transverse passage 98 in the piston. This passage linturn connects with a passage 100V drilled centrally of the piston rod26. The ball joint 24 at the antipumping end of the piston rod 26includes a flat portion 104- so that continu,- ous communication isprovided with thedrilledpassage 106 in the socket 22, regardless of therotary or tilted position of the piston rod in the pumping cycle. i

The bottomfor reaction facev (FIG; `2)Y 110 of; the unitary drive plate420 contains al plurality of circular` wells or recesses 112 which, asseen also -in FIG. 3,'may have their centers eccentrically located orspaced in an outward direction with respect to the axis of the bleedpassage 106. The wells or recesses 112 form pressure-balancing areaswhich form a liquid-type bearing surface to reduce the friction loadingon the adjacent cooperating plain bearing 120. 'f

The construction of the pump is such that there is permitted a limitedrelative laxial movement of the thrust drive 20 with respect to theVplain bearing 120 so that there is provided therebetween avariableorifice depending upon the 'pressure and the loading'of thepurnp parts;I i The pressure wells 112 and the'remaining radial areas of thejuxtaposed surface 110 and the bearing 120 form i 3 the total balancingforce depending upon the pressure across this-region. Thus, the maximumbalancing pressure will occur in the wells 112 but there is a dropacross the cooperating surfaces as the leakage flow passes outwardly tothe substantially low casing pressure. The total force is an integrationof the particular pressures over their respective areas which, at thebalanced position of the parts, are equal to the total force acting onthe piston heads. Thus, the variable orifice formed by the space inbetween the reaction surface 110 of the drive plate 20 and the bearings120 determines the outfiow of the bleed fluid and hence the pressurelevel necessary to achieve equilibrium and balancing.

For example, if the combined tiuid pressure in the well and between thecooperating surfaces is at a level whereby the force acting on thethrust bearing is less than the force generated by the piston, theunitary drive plate will be urged toward the thrust bearing andeffectively reduce the area of the variable orifice which effects areduction in fiuid fiow and hence builds up the pressure in the well andthe cooperating surfaces until the forces created by this newlyincreased pressure will substantially equal and cancel out the forcesgenerated by the piston. And conversely should the combined fluidpressure in the well and between the cooperating surfaces generate aforce which is greater than the force generated by the pistons, theunitary drive plate Will be urged away from the thrust bearing,effecting an increase in effective area of the variable orifice so astoincrease the flow therethrough and hence reduce the pressure in the welland cooperating surfaces. In this manner the movement of the unitarydrive plate with respect to the thrust bearing will automatically adjustitself to maintain a iiuid pressure level in the well and between thecooperating surfaces so that the forces generated thereby willsubstantially match or equal the forces generated by. the piston.

It is thus apparent that during starting, the unitary drive plate willbe moved away from bearing 120 so as to form a lubricant filmimmediately to avoid starting friction.

'The bleed Huid from the radial variable orifice can iiow through achamber 130 leading to the casing. Another passage 132 is provided forreceiving leakagel fiuid from the annular chamber 134 leading from theinside or axial end of the variable orifice.

Returning to FIG. 1, the radial pump forces are absorbed through anannular plain bearing 150` which engages an outer peripheral surface 152on the drive plate 20. The size of the bearing 150 is materially reducedby locating its supporting pedestal 154 in a plane containing thecenters of pivotation of each of the balls 24 at the antipumping end ofthe piston rods 26. In this way, the radial loads are symmetrical, thusavoiding any cooking tendency which would require larger and higherstrength bearings and supports. With this particular bearing arrangementand the pressure balancing, the size and weight of the pump of thisinvention are materially reduced.

Another advantage of the radial bearing described is that the rotor ofthe pump does not have to absorb these radial loads. Instead the sideloads are taken at the antipumping end of the connecting rods so thatpiston wear is avoided since they are not subject to eccentric loading.

In order to further reduce the weight requirements of the pump assembly,reference is made to FIGS. 3 and 4. As previously stated, the pressurewells I1?, which are disposed about the center of the unitary driveplate 2f) have their centers radially spaced from the centers of thebleed passages 106 leading'thereto. This moves the total center ofpressure radially outwardly s that on the pumping side of the thrustplate, the resisting force will be located inwardly thereof as seen inFIG. 4. This resisting force and the center of pressure produce a forcecouple which can be balanced readily by a relatively small balancingforce, as indicated in FIG. 4, because of itsrelatively large momentarin. It should be noted, however, that the center of pressure willtravel radially as the valve plate 60 is adjusted since only certainpistons will be contributing to the final pumping output. In any case,the center of pressure should be coincident with or outboard of themajor resistance vector.

As a result of this invention, it will be apparent that an extremelylightweight pump has been provided which can be made relatively small insize. This compactness makes it readily adaptable for aircraft andmissiles Where weight saving is of the essence. Thus, the bearings arereduced materially in size and weight permitting the entire structure tobe manufactured at low cost.

Although one embodiment of this invention has been illustrated anddescribed herein, it will be apparent that various changes may be madein the construction and arrangement of the various parts withoutdeparting from the scope of the novel concept.

I claim:

1. In a multiple piston pump having at least one pumping chamber, apiston in Said chamber, a piston rod extension for said piston, platemeans at the antipumping end of said piston rod, a bearing surfaceadjacent said plate means and receiving the reaction from said platemeans, pressure-balancing means comprising a second chamber between theadjacent faces of said plate means and said bearing, said second chamberhaving an effective area greater than said pumping chamber, a firstpassage means passing through said rod and including a fixed areapressure-reducing orifice connected to said pumping chamber and furthercommunicating with said second chamber, said orifice being formedbetween the wall of said pumping chamber and said piston, means forminga variable area orifice conducting fluid from said second chamber topressure balance the pump, and means permitting limited relativemovement between said plate means and said bearing surface for varyingthe area of said variable area orifice.

2. In a multiple piston pump having a rotatably mounted rotor, aplurality of cylinders formed in said rotor a corresponding number ofpumping pistons mounted in said cylinders, plate means connected to theantipumping end of said piston, a bearing member having a rst bearingsurface and a second bearing surface surrounding the first bearingsurface, chamber means located between said bearing member 4and saidplate means for receiving fiuid from said cylinders so that said fluidacts on said first bearing surface, passage means extending through saidpiston including a fixed restriction connected to said cylinders forcommunicating with said chamber means, said plate member being movablerectilinearly with respect to said bearing member for defining avariable orifice, said variable orice serving to control the leakage offluid from said chamber means so that leakage fiuid acts on said secondbearing surface, the combined first bearing surface and second bearingsurface serving to counterbalance the thrust force created by saidpumping piston.

3. In a pump having a rotatably mounted rotor, a pluA rality ofcylinders formed in said rotor, a corresponding number of pistonsmounted for reciprocating movement in said cylinders, a rotatable platemember, piston rods connecting said pistons to said rotatable platemember, a bearing member mounted in juxtaposition to said rotatableplate member and having both a high pressure reaction surface and a lowpressure reaction surface facing said rotatable plate member, passagemeans including a fixed restriction formed in said piston and pistonrods leading fluid from said cylinders to said high pressure reactionsurface, chamber means formed in said rotatable plate member locatedbetween said rotatable plate member and said high pressure reactionsurface, the fluid in said chamber acting against said high pressurereaction surface, said ro#4 tatable plate member being movablerectilinearly with re. spect to said bearing member to form a variableorifice, said variable orifice controlling the leakage of fluid fromsaid chamber whereby said leakage fluid acts againstV said,

low pressure reaction surface so that the combined high pressurereaction surface and low pressure reaction surface serve tocounterbalance the thrust force created by the movement of said pistons.

4. In a multiple piston pump having a rotatable barrel including aplurality of pumping chambers formed there* in, pistons in saidchambers, plate means connected to the antipumping end of said pistons,a plain bearing having first and second surfaces adjacent said platemeans and receiving the reaction from said plate means,pressurebalancing means comprising a uid chamber between the adjacentfaces of said plate means and said first and second surfaces, a firstpassage means extending through said pistons including fixedpressure-reducing orifices connected to said pumping chambers andfurther communicating with said fluid chamber for acting on said firstsurface, said plate means being movable rectilinearly with respect tosaid plain bearing for defining a variable orifice for controlling theuid from said fluid chamber to said second surface, said first yandsecond surfaces serving to counterbalance the thrust force created bymovement of said piston.

5. In a multiple piston pump having a rotatable barrel including pumpingchambers formed therein, pistons in said chambers, piston rods for saidpistons, annular plate means connected at the antipumping end of saidpiston rods, an annular plain bearing having first and second surfacesin juxtaposed relation to said plate means and receiving the reactionfrom said unitary plate means,

pressure-balancing means comprising a fluid chamber means between thejuxtaposed faces of said plate means and first and second surfaces,said` fluid chamber means having an effective reaction area greaterVthan the area of said piston, first passage means extending throughsaid piston including a fixed area pressure-reducing capillary orificeconnected to said pumping chambers and further communicating with saidfluid chamber means, and said unitary plate means and said unitary plainbearing defining a variable orifice controlling the flow of fluid fromsaid fiuid chamber to said second reaction surface, the uid in saidfluid chamber acting on said rst reaction surface, the combined uidacting on said first reaction surface and said second reaction surfaceserving to counterbalance the thrust force created by the movement ofsaid pistons.

References Cited in the file of this patent UNITED STATES PATENTS2,241,7011 Doe May 13, 1941 2,733,665 Klopp Feb. 7, 1956 2,834,297Postal et al May 13, 1958 2,901,979 Henrichsen Sept. 1, 1959 2,918,012Lucien Dec. 22, 1959 FOREIGN PATENTS 640,168 Great Britain June 29, 19481,114,641 France Dec. 19, 1955

1. IN A MULTIPLE PISTON PUMP HAVING AT LEAST ONE PUMPING CHAMBER, APISTON IN SAID CHAMBER, A PISTON ROD EXTENSION FOR SAID PISTON, PLATEMEANS AT THE ANTIPUMPING END OF SAID PISTON ROD, A BEARING SURFACEADJACENT SAID PLATE MEANS AND RECEIVING THE REACTION FROM SAID PLATEMEANS, PRESSURE-BALANCING MEANS COMPRISING A SECOND CHAMBER BETWEEN THEADJACENT FACES OF SAID PLATE MEANS AND SAID BEARING, SAID SECOND CHAMBERHAVING AN EFFECTIVE AREA GREATER THAN SAID PUMPING CHAMBER, A FIRSTPASSAGE MEANS PASSING THROUGH SAID ROD AND INCLUDING A FIXED AREAPRESSURE-REDUCING ORIFICE CONNECTED TO SAID PUMPING CHAMBER AND FURTHERCOMMUNICATING WITH SAID SECOND CHAMBER, SAID ORIFICE BEING FORMEDBETWEEN THE WALL OF SAID PUMP-